1. Field of the Invention
The present invention relates to a fuel container containing liquid fuel and to a fuel residual amount measurement method and device for measuring the residual amount of the liquid fuel.
2. Description of the Related Art
Over recent years, remarkable progress and development have been made in the field small electronic devices such as mobile phones, notebook personal computers, digital cameras, wrist watches, personal digital assistance (PDA), and electronic notes. As power sources in such electronic devices, there are used primary cells such as alkali dry cells and manganese dry cells, and secondary cells such as nickel-cadmium storage cells and lithium ion cells. However, from the viewpoint of energy utilization efficiency, it cannot be said that effective utilization of energy is normally implemented in the primary cells and secondary cells. Nowadays, extensive research and development are in progress for fuel cells that are capable of realizing high energy utilization efficiency as alternatives for primary cells and secondary cells, as described and shown in Jpn. Pat. Appln. KOKAI Publication No. 2001-93551.
A fuel cell as described in Jpn. Pat. Appln. KOKAI Publication No. 2001-93551 is configured to include: a fuel cell body configured such that an electrolytic plate is interposed between a fuel electrode and an air electrode; and a fuel container which contains a liquid mixture of liquid fuel such as methanol, and water and which is connected to the fuel cell body. The fuel container is formed with a discharge port through which the liquid mixture is supplied. When having been empty, the fuel container can be replaced with a new fuel container.
Recently, it is desired that the residual amount of liquid fuel in a fuel container is measured. In this case, however, a sensor is necessary that detects liquid fuel existing in the fuel container to measure the residual amount of the liquid fuel. In this connection, suppose now that the fuel cell described in Jpn. Pat. Appln. KOKAI Publication No. 2001-93551 is mounted in a small electronic device as mentioned above. In this case, since the electronic device and the fuel container are used in various posture and directions, so that the liquid fuel flows to various positions corresponding to the posture. Consequently, the liquid fuel existing in the liquid fuel cannot be sensed by the sensor, and hence the residual amount of the liquid fuel in the fuel container cannot be measured.